My guess as to the order of things:

Late this month we learn who the buyer is.

At the same time, we get enough of the nuts and bolts of the transaction, that we know what conditons have to be met for closing, which is still anticipated to be in September. 

So, to me, that means that the key condition is that we need to show that the interposer works as anticipated and to the satisfaction of those who are potential first customers.  If that's not the case by September, I doubt the deal closes then, it will wait, or at least any meaningful transfer of the buy out consideration will wait, until the buyer is satisfied. I don't know this will be a condition of closing but I can't imagine it will not be, unless it's already been satisfied by the time of the reveal.

Could there be an extension of time for satisfaction of the prove out of the IO, of course, but they'd better be pretty close and inspire confidence that it is ONLY a matter of time, rather than a "fourth terminal" type issue. 

The bigger (more recognizable) the name of the buyer, the better off we will be at the time of the big reveal of the buyer's name.  I expect a rise in price with a well known suitor, but whatever conditions there are to be satisfied will play heavily on our price.