You could still get the cloak quest done I believe. You still have 2 months until WoD launches. As long as you start the quest (I believe), you can still finish it in the time between 6.0 and launch of the xpac. They're removing the Valor part when 6.0 hits which is the big timesink. For the SoO mount, you'll probably have to pay unless you know someone in high places (
http://us.battle.net/wow/en/forum/topic/14277497821). You can still get the challenge modes done. Your gear gets scaled so its more about getting the right gear than getting the best gear. Download something like oQueue and try to find a group. That is going away with 6.0 though, so it's more of a tight timeline. People also pay to get carried through that.
Do what you enjoy though. The cloak will be 'worthless' at level 100. There are a million other transmogs and mounts you can leisurely try to get. I watched a video about things to do to prep for WoD. Alts were highlighted. Because of the way garrisons work, there are some nice benefits to having multiple garrisons going. All that said, I'm trying to get my cloak quest done, but I have most of it done.