Well, this is probably the first year in a long time when I'm not really hyped for E3 because I have doubts any of these conferences would be really decent.
Bethesda - nothing interesting except Doom Eternal
Microsoft is already working on next gen, so I doubt they will have lots of new games shown this year unless they are really moving to that "beyond generations" strategy. If that neogaf leak is true, then this conference would be pretty boring IMO.
Nintendo - from the past few years, it doesn't seem that they take E3 really serious. Most of the interesting game announcements they do on their own directs throughout the year, so most likely E3 will be just a gameplay showcase for early announced games with a few new surprise announcements.
Square Enix - the only thing I'm interested to see from them is FFVII Remaster.
LRG - I always seem to skip their conference somehow. Probably they will show something interesting but I don't remember any big announcements from them for the past years.
PC Gaming Show - last year I fell asleep halfway through it. Don't see any big changes in this for this year.
Ubisoft, EA - not interested in these publishers games at all. But last year. Ubisoft at least had some funny moments so it was interesting to watch.
So, in conclusion, if I were to choose the one which is most anticipated, it would be either Devolver, because their conferences are the state of art or probably Microsoft for some big third party game announcements as Microsoft is the only conference this year where big third party games announcements can happen. But considering that most of developers are probably switched their focus to PS5/next-gen Xbox, I don't really see many announcements happening this year. So, I'll go with Devolver.
Of course I will try to watch every conference this year just like I did last year, but not setting my expectations high. Next year should be really big though.