Windows Phone 8 will not be coming to the current crop of Windows Phone 7.5 devices.
Instead the current Lumia 800 and 900 and those from other manufacturers will be getting Windows Phone 7.8.
This will include screen layout changes among other things.
There is so much technically missing from the current Windows Phone 7.5 devices that I believe people didn't buying into the device for it's feature set and probably not really bothered with news of updates or not.
The good news is that the current range of Windows Phone 7.5 devices should be considerably reduced in price as the likes of Nokia attempt to boost the current volume of sales until Windows Phone 8 devices come on line.
The current Lumia 800 and 900 are still nice looking phones (I think so) and if your main use is txt'n and phone calls with a bit of social media the Lumia 800 and 900 are great. A bit over priced, but that should change now.
No Android geek would be paying top dollar for Snapdragon S2 chipset devices, when most Android phones where using the Snapdragon S3 when the Lumia range was released and at that time, some Android devices even had a Snapdragon S4 in them.
I suggest (A rumour I just started right now) we'll probably see the new range of Windows Phone 8 devices sporting a Snapdragon S4 chipset, which is a giant step forward from the Windows Phone 7.5 devices we currently see.