If that's what happens (just for the sake of argument here) WotC would call it a very big win and feel pleased with themselves, because there's a hell of a lot lot more people out there who are 'meh' or negative on psions than there are hardcore psion fans, and if they could satisfy the former, then disappointing the latter is a price they'd cheerfully pay. WotC want a psion that satisfies people who pick up Tasha's, read about this 'psionics' thing, and decide to give it a go.
One thing us old-school types have to remember these days is that we are no longer the people who WotC are primarily designing products for. The target D&D 5e market in 2020 is aged 14-27, learned about D&D through Critical Role or Stranger Things, and has most likely never even heard of psionic defence modes or metacreativity. If WotC can throw us a bone while they cater for their main target audience, they will, and WotC have no shortage of creatives who cut their teeth on 2e/3e and love the settings etc so they will do that whenever they can. But all that is secondary. 5e WotC will always keep their majority focus on the majority market segment. And that's just not the people who played old-school psionics any more.