No one bit, combination of 3 factors. It would involve either major redevelopment of the existing stadium or complete demolition and start over. Where would we play in the 1-2 years whilst this was going on? Tannadice? Dens? fuck that. There's also no money from the sale of the land and educated opinion on modern stadium standards says we would end up with nearly half the current capacity. Again, fuck that. Overall it just doesn't seem worth pursuing to me. The bang to buck ratio is far higher with moving than it is remaining, location seems a fairly small price to pay imo.
There's a very obvious one. It will be a fair bit cheaper to build training facilities as part of one complex then on two sites.