Sure when you first finally get some it's such a great thing but just like most everything else it will come to pass. I would love to see GW get really creative with the new Space Marine codex. It is time to break the mold and right now is a better time than ever. Lets face facts - tactical Marines really blow hard. A full squad is over costed for what you get and a combat squad dies to a stiff breeze. It's just the way it is. One of the reasons why Blood Angels were relevant in fifth edition is the ability to take cheap assault squads as a troop choice... This could be a good starting point to fixing Space Marines - bring them back up to the top again. I think this would be good for the game.
I'd love to see an option for tactical Marines to take unit members with two bolt pistols in lieu of all bolter-bolt pistol-chainsword/special weapon/heavy weapon. Mix it up for some potent combos with some bolters and special weapons. Heck let them take a second special weapon in exchange for the heavy weapon just like Chaos Space Marines. Redefine vanilla Space Marines - You must have solid low cost troops to be competitive. Don't be afraid to make Space Marines totally kick ass again. I'd love to see suspensor belts for the dudes lifting heavy weapons so they can move and shoot at full ballistic skill - cut the range in half if they scoot and shoot.
To me Tau have redefined the game. I want to see other new armies do the same thing. All the old canon has been swept aside. It's time to do new things. That's all there is to it.