Oh my! A few days ago I said in another thread that we can expect to hear news of the next update soon, and here we get our first teaser photo.
Hmm... "I expect to receive small dollar donations from everyone on the forum." (It's worth a shot, eh?)
Still too soon to know for certain if it'll be 1.8 in full. The only thing from 1.8 we see is the different fence types. For that matter, we don't even know if we'll get 1.7 in full since all we see is Stained Glass.
How would these additions alter the texture packs? I downloaded a few different ones, so if they added stained glass, would they automatically alter those in say Skyrim or would either I need to update the texture pack or they simply would not be added to them?
The textures for new blocks will be added to the texture packs. Most likely, they're already in the texture files waiting on the blocks to be added. Wolfhusband is probably correct in that no changes will be made to the Mash-up worlds themselves though.
Last time new blocks were added to the game (e.g. Hardened Clay) all the TPs were automatically updated. Like Urban said, it's likely the textures are already included in the TPs themselves... they just need to be assigned to a block.