There really is no answer to that. No two rigs are ever the same when it comes to maintenance, the driving styles it's various owners and if you end up with a faulty component. There are numerous folks that have had early Jag engines pass 200K miles. I think you would be hard pressed to see 300K without some major rebuilds involved. In theory any car can last indefinitely if you sink enough money into it.
I'm interested in this as well. I just picked up a 2006 RR Supercharged with 100k miles from the local Land Rover/Jaguar independent mechanic. This rig will serve as the backup to my 01 Tacoma TRD (or should it be vice versa) so it won't get many miles put on it, maybe 3k miles a year.