I think the potential inability for RedBull to get adequate engines is scary. Also, from the James Allen article, supposedly, Mercedes engines can now be ruled out definitely. This means it's either Ferrari or RedBull will potentially pull out with two teams, as I think there is an understanding that Renault will either continue as a works-team with the purchase of Lotus or not at all - as continuing as an engine supplier is apparently not an option.
If all goes wrong - that is, Renault fails to purchase Lotus and RedBull fails to either get or want engines from Ferrari, we could perhaps see quite an empty grid next year. It probably won't go that far, and publicly, Ferrari seems happy enough to supply RedBull and Torro-Rosso under the assumption that the contract with Renault can be successfully terminated.
I must say, I'm a bit disappointed that Mercedes will not supply RedBull. Understandable of course, entirely, but I would have loved to see how competitive such a RedBull could be. I know some here think Mercedes is a class of the field not only because of their engine, but also because of their chassis, but I still think RedBull has not lost it and are compromised precisely because they are dealing with an underpowered engine and are finding themselves outside their comfort-zone. Even with a Ferrari engine next year, things will be very interesting, at least, under the assumption that Ferrari can close that gap a bit more.