It will be supported, Dice is REALLY good at that. Not only did they fix most of the issues with BF4, but BF:Hardline released in a much, much better state.
There will be the season pass, but this will have a ton of content. Not just map packs, they generally also add more weapons, vehicles, etc. Plus these aren't CoD sized maps, these are from 4x CoD sized map to 20x the size. So they really are good maps.
But on top of it, do you see how Dice is supporting BF4? They are releasing more maps, for free, still now and in the future, and the season pass stuff was done over a year ago.
So yeah, they probably will support this game quite nicely.
Oh and in case no one has found out, they extended the beta another day!
I don't think they really wanted to take out space battles, I just don't think they have the development time to do them. Think about it, the license was just given to EA/Dice to work on not that long ago. Many games have 3-5 year development cycles. Not only that, they have to make sure it adheres to the Star Wars Universe (a success), make it different from Battlefield (a success), tie it into the new movie with the Battle of Jakku free DLC for pre-ordering, etc, etc. Thus they didn't really have the time to do the space battles.
I wouldn't count it out in the sequel, but this time around it's about getting their ducks in a row, making it good for what it is, and launching this fall near the movie release. Not really a mistake, more of a decision to limit the scope given the real constraints they faced to ensure quality and timeliness.
Also it is possible to defeat both AT-AT's on the first Y-wing raid. I've been on a team that has done it a few times. Also the Snow Speeders on the 3rd and last Y-Wing raid can take out both AT-AT's even if you haven't been able to damage them one bit up to that point. You could have each of the snow speeders take one AT-AT out, OR you can actually have one snow speeder take one out, and then take the other one out. It's very winnable from the Rebels side, you just need people to know what they are doing, and a beta isn't a good place to find knowledgeable people about a brand new game. (and also because it's free, and it's got the pull of star wars, you got a lot of people who have never played a multiplayer shooter before in these games)