Microsoft have release Windows Phone 7.8 in the last few days. As usual the rollout appears to be phased, I think based on serial number of your phone. As with previous versions you can force the update, so jumping the phased rollout queue. The process is
- Put the phone in flight mode (so no data connection)
- Connect it to your PC running Zune, it will look to see if there is an OS update. If it finds it great, let it do the upgrade
- If it does not find it, select the settings menu (top right in Zune)
- You need to select the update menu option on the left menu
- Zune will check for an update, about a second or two after it starts this process disconnect the PC from the Internet. This should allow Zune to get a list of updates, but not the filter list of serial numbers. So it assume the update is for you.
- You should get the update available message, reconnect the internet (it needs to download the file) and continue to do the upgrade
You will probably have to repeat step 5 a few times to get the timing correct
I also had to repeat whole process 3 three for 3 different firmware and OS updates before I ended up with 7.8. But now I have multi size tiles and the new lock screen.
Or if you don’t fancy all the hassle you could just wait a few days