http://articles.businessinsider.com/...s-nt-microsoft

it's named after this
http://en.wikipedia.org/wiki/Windows_Runtime

If you are asking why Windows on ARM was named after Windows Runtime and confused the hell out of everybody, then I don't know but the RT stands for runtime according to MS, not real time.

says the guy who said the following with certainty and with added emphasis:

You are right I don't know for certain what 7.8 will include, they may just invest in a large development team to bring the same experience but I'm not holding my breath, I'm going by what has been confirmed so far and making an educated guess. So far WP7.8 is just a start screen addition.

http://www.youtube.com/watch?v=-c_vk0UnlIk&t=1m45s

I suspect, and I guess I should have made that clear, that there will be little effort to develop everything they do in WP8 for WP7.8.

If you want to place bets I will even be specific about features I suspect will be missing from 7.8:

No Skype over lock
No Encryption
RTC Alarm wakeup
Limited Multitasking in WP7.8 in comparison to WP8
No Separate volume controls

We can come back and look at this when 7.8 releases.