I say take a page outta the 2024 ranger in that regard. You get the perks of Hunter's Mark applied automatically to your favoured foes. If you want that bonus against everyone else, then that's a Hunter's Mark spell following normal spellcasting/slot rules.
Why would I want to do that? Mine is simpler and better, frankly, IMNSHO. Especially since if my Rangers want to use concentration for the spell, they can cast
hunter's mark on a favored enemy or whoever for the damage buff.
5.1 is a transition period. WotC was experimenting with new rules that would eventually become much of the 5.2 design changes. Thus it made sense to me that if you preferred the Type of changes Tasha and later made (custom ASI, level 1 feats) you'd be more inclined either keep going to 5.2 or to an adjacent system (like Tales of the Valiant) which made similar changes. Whereas if you did not like those design choices, you would return back to stock 5.0. Eventually, you won't see much 5.1 era games, people will either upgrade to the never things or curate them back.
Now obviously there will be exceptions. People will mix and match and build chimeras probably more often than not. But I think as time moves on both camps will become a bit more solidified and 5.1 will functionally cease to be played and 5.0 and 5.2 becoming the division line.
I don't think a roughly 60/40 split is enough deviation to justify anything, especially concerning the larger hobby base outside of this forum.
I mean, this wasn't revoluntionary or anything, right? Tasha's came out, a lot of people liked it, some didn't. Pretty much things since then have moved in that direction--we all saw that coming... So, how shocking is it that those concepts or changes implemented in Tasha's and forward made it into the 2024 edition? Not surprising at all IMO.
For the roughly 40% who currently are sticking with post-Tasha's 2014, the reasons people have mentioned suffice. Waiting for the final core book or further supplements, don't have the cash for something that is basically the same I already have, etc.
Many of that 40% IMO will move on
eventually like you said, but some will remain just where they are and be happy about it. I don't think it will only be a "go back" or "move on" split for that 40%. Another reason is they have Tasha's and beyond already, and will explore other systems, returning to the 5.1 point when they return to D&D. For some, they just don't have a compelling reason to move on, and for many we definitely have a compelling reason for going back.
