In 5.4, TOT will become cross-realm. The other thing is that TOT was been fairly difficult for casual guilds, a lot on my server still aren´t clearing it. More than likely they will continue to run it when SoO launches.
Yeah, we will have to see which way it will go. As others have said, despite the Cross-Realm stuff and the changes in 5.4, it is possible there will be less of these pets about. I think there will be less ToT runs overall in 5.4, and quite a lot less. There will be a lot of pug runs, but not as many runs as there are currently. Also, the problem with this pet is that anyone getting into a pug in 5.4 because of this pet will learn it instantly and it won't turn up for sale on the AH.
As for getting the gold across to another server, what I did was buy a couple of Banana's and one Dragon Kite when they were up on the BMAH on my low pop server (where all my gold is). Then I caged them and sold them on a level 1 I created on a very high pop server. That gave me enough gold to pick up the Viscous Horror and a few TGC pets. I also pick up any other pets on the BMAH when I can (Crimson Whelp, Disgusting Oozling etc) for the same reason. It's an easy way to get gold across. Oh and I sometimes pay a little over the odds at the BMAH, just to make sure I win. It is worth it if it means you can transfer the pet over. All that gold on a server with not many decent pets for sale is an issue! This solves it without the need to do Character Transfers or a Guild Transfer.