I'm not at the stage of selling mine, but i see no point in buying BoM until there's actually some in game content.
A few more planes and another map doesn't matter much when you cant do jack with them.
I laugh at the Devs claims back in Alpha how we were going to have a fantastic offline experience, there is precisely none except for crappy disjointed unlock bollocks missions billed as a campaign. BoM is just another bit of revenue off the fanbois for them, we'll see if anything actually changes (hopefully) or when this mythical fmb might drop (god only knows why its taken so long)
This game desperately needs an fmb to do something with it and then the community might be able to inject some substance into the game, not that we'll be seeing co-ops anytime soon either, and yes i saw Zak's comments, but since we've supposed to be getting the fmb for as long as i can remember, i scoff at that.
Its like they've almost tried too make the most stupid decisions to ruin their what could be a good game.