Marussia are going to miss the US GP too due to financial issues. At that point they're on the slippery slope, so I wouldn't expect to see them again.
What a fucking sad state Bernie's greed and incompetently short-sighted management of the sport has brought us to. He's so busy shoving all the money he can find up Ferrari's mid-field arseholes with his special deals for the teams he arbitrarily considers "important" that there's no business model that works for the bottom half of the grid. And without the bottom half, the second quarter becomes the bottom half.
Teams won't run three cars because it's 50% more car, more transport, more staff, more parts, more engine usage, and no sponsor is going to pay 50% more for one more car. Is Bernie going to pay 50% more prize money once they run three cars? Sure. His pet unicorn will come right around with those bags of cash.
The three car teams idea is a slippery slope in itself anyway - once the top 10 is entirely locked out by 3.333 teams, more teams will go bust. So what, four car teams? Five? Might as well go single-make-spec-series.
F1's been teetering on the edge for a while. Depending on how the next year goes it could die all together as we know it.