I'd take a bet that wheel horse parts will be available for way more than 10 years. Real Gravely tractors haven't been made in years and were never a huge seller to begin with so you will have a harder time getting parts for them.
Back on subject, I'd take a look at some of the Mahindra and Kioti forums. Seems like many people complaining that dealers are disapearing in their area. If you have a well established dealer that will be around for awhile then I say shop away, but be careful buying from the used car/ imported tractor lot that may be closed in three weeks. I'd also recheck some of the more established lines. Often it is a misperception that they are priced way more than the new imports. Many times you can get them for close to the same amount of cash.
For example.
The TYM 450 is sync gear tractor with 45 hp and 38 pto hp. It has hydraulic flow of 10.94 and three point hitch capacity of 2105# at 24".
I'm not sure exactly what you would have to pay for it but I assume it is around 20k since this is your budget.
A new Holland TC 45 A is also a sync gear tractor with 45 hp and 39.6 pto hp. It's hydraulic flow is 14.9 and three point hitch capacity is 2330# at 24"
I got a quote from a national retailer for:
TC45A 4WD with R4 tires and Deluxe 3 point hitch and folding R.O.P.S. - $17,600.00
with 16LA Loader add $4,200.00
And just for kicks the larger tc48 is:
TC48DA 4WD 12x12 Transmission with Ag. tires - $18,900.00
with R4 tires add $300.00
with 18LA Loader add $4,800.00
These are both close to budget and I'm sure with some shopping a comparable Kubota, John Deere, Massey Fergusen could be had for comparable $ if not less than this.
Again, I'm not saying not to buy a TYM, but I'd be for damned sure I looked at all other possibilities first.
Also, as for the fact that Kubota was a import start up 20-30 years ago and look what happened to them. Well the same could be said for many other brands like Belarus. Where are they now? Kubota was the exception to the rule of a brand lasting as long as they have.