To start a conversation on why Jurickson Profar should not considered as a long term solution at 1st base, it is important to consider positional adjustments. Positional adjustments are an important part of evaluating players and building teams due to the principal of opportunity cost. Opportunity cost is the tradeoff of what assets you are giving up by acquiring or keeping a different asset. In baseball this directly relates to positional adjustments due to the differences in mean offensive production from different positions. Jurickson Profar is a perfect example; assume Profar has a long term career at SS while keeping a wRC+ of 110. The average wRC+ at SS is 85, so Profar is ~29% more valuable with the bat than the average SS. If he has to move to 2nd base where the average is 91, he is only ~21% better with the bat than average. Here is a chart of wOBA by position as of 2014 from Fangraphs:
Opportunity cost comes in to play when you consider the implications of the data; the opportunity cost of playing Jurickson Profar as SS is statistically significantly lower than playing Profar at 2nd base due to it being easier to find a 2nd baseman who can hit at that level than it is to find a SS who can do the same. In addition there is another opportunity cost due to the disparity in value of Profar at 2nd and the value that other teams would put on him due to him being able to capably handle SS.
In a vacuum a team would play the players with the highest offensive and defensive value at their positions while trading the players who have no slot on the team for their equal value in positions that do have a spot. Obviously this is not the case, but it is relevant to the current situation due to there being four Ranger infielders vying for three open infield spots. Also Jurickson Profar provides value currently at first base due to there being few viable alternatives, so this breakdown is completely about moving forward in the future.
A popular idea that has come up with Jurickson Profar's immediate success and aptitude for playing 1st base is to have him be the long term 1st baseman. Jurickson Profar is projected to be an above average hitter, but not too much above that. Assuming he plays 1st base with excellent defense and an above average bat he would simply be an above average player. It would not be hard to replace his value at 1st base due to it being statistically easier to find above average hitting 1st basemen. This would be a massive waste of resources due to his trade value at SS being so high compared to his value as a 1st baseman. The other cost is the risk that Joey Gallo will not be playing at 1st base going forward.
It could be argued easily that Profar might be the more valuable player between him and Gallo going forward, but ignoring Profar's ability to play a premium defensive position there is not much justification for that argument. Even as the #1 prospect, Profar's optimistic future offensive projections were along the lines of .280/.370/.430; good for a ~.800 OPS which would put his wRC+ around 111. Meanwhile Joey Gallo is often given likely offensive grades of 40-45 hit/80 power. Assuming he walks in 10% of his PA's (17.6% in AAA this season) that line would be around .240/.330/.540 which would be good for a ~133 wRC+. Once you add in the fact that both Gallo and Profar project to be solid defensive players at 1B with Profar having the slight edge it becomes hard to justify keeping Profar there over Gallo. The gap widens when you consider that Profar has 3 fewer years of cheap control and the potential ceilings of the two. Gallo's insane power and solid approach suggest that if he were ever to sustain a .260+ batting average (which some scouts think he will) over the course of an entire season he would approach MVP levels of production. Profar's offensive ceiling is still very high as 2016 Ben Zobrist would be an accurate representation, but it wouldn't come close to the numbers that Gallo is capable of putting up.
The problem the Rangers are trying to solve is probably not between Gallo and Profar, but rather trying to find a way to maximize the value from their four young controllable infielders with three open positions. Due to the nature of what was discussed earlier, I think the Rangers will see one of four potential possibilities come to pass in this order of likelihood; Jurikson Profar is traded, Profar and Gallo keep expanding their positional versatility and the team runs with a "super utility" player in the future, Rougned Odor is traded and Profar moves to 2nd, or Elvis Andrus is traded and Profar takes the SS position. It is very unlikely that Joey Gallo gets traded in order to let Profar take the spot full time unless there is a trade that massively favors the Rangers in terms of value.
Either way if it comes to pass that one of these young kids has to put on a different cap one day I am going to be inconsolable as I eat ice cream out of a Ranger helmet watching these videos.