I can't see them acquiring EA let alone Valve. Valve is a private company and Gabe has turned down multiple attempts from deals like that before. EA makes their own piles of money, so I don't see it happening on their terms.
PuB is 50/50, though the studio has turned down the previous offer from being bought out before. Even if they were bought out, it'd mean the studio would end up spamming the same kind of games until popularity dries up and they get put out back and shot.
If they ever bought out Valve, I'd probably revert to GoG/Battle.net entirely. MS has tried to control PC gaming for years and it's always backfired and proven that they really do not care for what PC gaming stands for, let alone what it's gamers want. Them buying out Valve would mean a the undoing of what Steam/Valve brought to the table, and a reversion of PC gaming in general.