4 months. July-November. Not alot of changes you can make based on feedback in 4 months. You can tweak damage values for weapons and health values for shields maybe, but it's not enough time to make any radical changes if people end up hating the beta gameplay. It's a gamble to wait so long to do a beta, if people like it you're golden, if they don't though you're totally screwed and have to delay or else have bad multiplayer that people hate on launch.

Here is another problem with waiting on July that I hadn't thought of. There is this common belief that early gen Xbox exclusives running on Series X are going to look worse than early gen PS5 exclusives because they are held back by forced cross-gen status for 2020 and 2021. If that belief is wrong, MS needs to come out and show that the next-gen versions of early gen 1st party games like Halo Infinite, Forza Motorsport 8, etc. look absolutely gorgeous and just as good as Sony's PS5 exclusives, before Sony opens preorders. If they wait to show that, people are going to be like "hot damn those PS5 games were gorgeous, and Microsoft is too scared to even show their 1st party games so they must look like ass thanks to cross-gen, so I guess I'm getting a PS5 first, I'll just play these cross-gen Xbox games on my Xbox One instead".

Here is the problem as I see it:

Early June comes, PS5 reveal show happens. Sony reveals the console design, a bunch of games including AAA juggernauts like Horizon Zero Dawn 2, and the price and opens preorders almost immediately after the show. Some people who were considering buying Xbox Series first instead of PS5, see the reveal, see the games, and see that preorders are open, meanwhile Xbox has no first party games revealed (aside from those they already showed like Halo and Everwild) and no preorders, so those people who had been considering Xbox Series first are like "well I wanted to get Xbox Series first but now they're a total no-show and these PS5 games look cool, guess I'll preorder PS5 instead".

MS absolutely should not let that happen. They'd be better off going with 3 events. Do this 3rd party one in early May, then maybe a 30-45 minute one in late May where they reveal Series S and show launch window and early 2021 1st/2nd party games. Then wait on the Sony June event, where Sony will presumably announce price and open preorders, then MS can respond immediately by giving their own price outside of an event through Xbox Wire and open their own preorders. Then a few months later around Gamescom they can do a 3rd show where they show new material for their launch window and early 2021 games, and announce the rest of the 1st/2nd party games, those that are releasing late 2021 or 2022. 

Details on the Summer event next week.