This is indeed a boss move by Microsoft and it is
possible that some of the big games will still come to PlayStation down the line (i.e. Elder Scrolls, Fallout etc). But to the question presented by the OP, PC will be a great fallback if I really wanted the Bethesda fix.
In the short term, I only really care about Deathloop and Doom Eternal (DLC and Next Gen Update). All of the those should still come to PS5 by next year so I'm good there. The only other game in the Bethesda staple that I would really want to play is the next Elder Scrolls game which is still years away. If it happens that it doesn't come to PS5, then I may just get on PC.
Again, boss move by Phil and team but it really doesn't do anything in the hear and now to make me want to get an Xbox over a PS5. If the Starfield, the next Elder Scrolls, and the next Doom game look amazing in 2-3 years, then I will surely look toward my PC or purchasing an Xbox console at that time.
At the end of the day, Microsoft is desperately trying to add more compelling content to GamePass and now with EA Play and Bethesda's portfolio they are going balls to the wall to increase its value...and they are succeeding