1.5 + mods in a nutshell:
Eloraam will update in 1.7, + 200 bugs and 2-3 new features, then disappear again till like 1.9
Thaumcraft will change everything again, also in 1.6 and 1.7, lets see what thaumcraft 10 has to bring us in the future!
IC2 will have the same exact stuff, nothing new as always.
You will need UU matter to craft the matter fabricator.
Instability of mystcraft now might give you viruses on your pc, and to be able to make a stable age, you will need to specify what blocks to use at what Y level, make your own caves and then place them in pages, etc.
Stell in railcraft now will take 1 minecraft day to make, and high speed rails will blow up stronger than never before
200 new species of bees that are just needed to breed other bees
Solar panels now require dragon eggs to make because they are so op
Buildcraft will invent something weird and new, sorta like lasers of the assembly table
Xycoridite will now be as useful as dirt, really good for growing stuff on them, besides storing lava in wooden tanks like is nobody's business, oh, and powering footballs with lasers, thats for sure!
Every FTB modpack will be laggy as hell, as always, even with a NASA computer.
Voxelmap will show you mushroom islands near by, and ever ore in a cave if you choose, or chests, sorta like nodus
you will be able to add everything to a turtle with misc peripherals, hell, shears and tnt...
turtles will cook food... oh wait they already do that... what about kill the wither... they do that too... they will play the game for you!
You will have molten of every item in game and be able to put it in a frame of whatever to make a new TE item
EE will let you exchange cobble for nether stars
Extrabiomes will have 200 more useless biomes so you wont be able to find that extreme hills for emeralds for your tinker table
Modular powersuits now will cook your food, walk for you and kill for you
Portalgun will now require you to be at the farlands, have 200 spawners near by and 29 activated beacons to make 1 gun
Reliquarry will now have 200+ guns like battlefield
(This is a joke, as people might not get it)