Unless that phone is all-existing-phones-killer, I pretty much dubt it will change anything.

Given the recent developments since February, it is even uncertain which OS will it use?

Given the overall strategy, and assuming that the phone is really something extraordinary compared to anything we have seen so far, I would suggest that WF7/8 will be the primary OS, with possible Meego/Harmattan alternative.

That would more likely influence the stocks. The release of Harmattan itself, would simply announce the technology, without providing the large deployment, so sooner or later the others will present their own magic and the advantage would be lost. The loss of advantage would reflect on stocks again.

Again, if they do have the technology advantage, they better apply it as soon as possible.