TBC Classic absolutely matters for SL, at least its launch date does. The ongoing phases won't matter much, but TBC Classic launch will be a spectacle as Classic launch was. They will not release TBC and 9.1 within <4 weeks. And as of now it looks more likely that TBC will launch before 9.1 sees the light of day. Mid March is over and we haven't heard any news of 9.1 or seen anything more from it. We're heading towards a June release date for 9.1 which is 7 months after SL launch. I often do not agree with Dracullus, but here I do. TBC is Blizzard's biggest factor for revenue in 2021.
And 9.1 sets the pace for the expansion in the sense of the later 9.1 comes the less time is there for huge content patches with raids like .2 and .3. Content patches without big raids? Sure, like it was in MOP. But huge patches like in Legion? Doubt it. The next expansion will inevitably launch later next year (because it's their only constant generator of huge revenue spikes) and that's the limiting factor for everything in between 9.0 and 10.0.
An average of 6 months for content patches, that means .1 to .2 or .2 to .3. Not .0 to .1 as the expansion launch is no content patch. Please go over WoW's patch cycle as I did and check for the launch dates. Content patches that contain raid tiers last for an average of 6 months mid expansion, final content patches are always longer than that, averaging 9-10 months.
And I don't make stuff up. Again, go back and check WoW patches. Check 4.1, 5.1, 6.1, 7.1 and 8.1 and compare them to 9.1. And then compare 9.1 to 8.2 or 7.2 and you'll see that 9.1 is way more in the style of 7.2 and 8.2 than it is of 7.1 and 8.1. Do you agree or disagree that 9.1 looks more like 8.2 than 8.1?
By the way, there's a nice article from massivelyop about 9.1 titled
The long wait for patch 9.1 in World of Warcraft:
https://massivelyop.com/2021/03/19/w...d-of-warcraft/ - it's a nice read a it lays out many points I brought up.