[KevinDonae]

I can see a HRT-PURE or a Virgin-PURE on the grid in 2013 but not much else. I don't think Williams or Sauber would be desperate enough to sign with company that has never designed an F1 engine before, even if they were extremely cheap.

I don't think you can make that claim all that easily:
http://www.autosport.com/news/report.php/id/91107
"Mecachrome will be putting together, manufacturing and constructing the engines - fabricating them. The development is being done by TEOS, IFP and D2T. So we are a very tight team, and being tight means that our costs are an awful lot lower - and that means we should be able to carry over this cost reduction to teams and give them a cost-effective power train."
PURE's engine design is being led by Jean-Pierre Boudy, who worked on Renault's first prototype turbo-charged racing engine in the 1970s and was responsible for Peugeot's F1 engines in the '90s. Pollock added that all the personnel on the project have F1 or Le Mans experience.

It sounds from the outset that this could be a properly well thought out campaign to build engines with a two year lead time.

It might be worth remembering that neither Techniques d'Avant Garde or Porsche had had much experience in building F1 engines, yet after 5 seasons they walked away with 3 Driver's Championships, 2 Constructor's Championships and 25 GP victories.