Extending tilt is all very well, but a lot of people do get sick, or at least feel sick on Pendolinos. Extending the sphere of tilt operation wouldn't be good for these people. Tilt is so last century.
Tilt Nausea is something I have felt from time to time but not all the time. I think it depends where you are sitting on the train and what sections of route. With regards to the route, I feel it more on the twistier sections north of Oxenhome and north of Beattock especially if I have been looking away from the window. The brain does funny things to you when you look up from a phone or book and suddenly become aware that the world around you is at a weird nine degree angle from what your eyes epect to see.
As for the future of Tilting trains - If we take Italy as an example - there are lots of routes where slightly higher speeds are allowed for tilting trains, but the stock is not most people's favourite because it tends to be smaller and more cramped. The older ETR485's feel very tired now and reports that their tilt mechanisms may be disabled are not verified. The newer ETR600's look nicer from the outside, but are more like a Voyager from a passenger point of view. The swiss versions are my favourite of the lot for interior comfort.
There now seems to be an emphesis on building new high speed lines - as much for capacity reasons as well as tilt. The Adriatic route upgrading is an example of that. In the last 15 years, Trenitalia has been running purely non-tilt stock on an almost hourly basis along the Adriatic, where tilting stock could have cut some time - maybe 30 minutes or so off the journey between Bologna and Lecce. The current upgrading works are seeing non-tilt speed limits raised to 200kph in places and the speed limits along those upgraded stretches of line are the same for both tilt and non tilt stock.
Another example is the route from Rome to Bari and Lecce. Currently it is served by ETR485 tilting trains, utilising their 250kph capability on the 300kph Roma to Napoli high speed line as far as Caserta, but once off the high-speed line, the timings between Caserta and Foggia are barely faster than non-tilt stock.
This is mainly due to the fact that CAserta to Foggia is mainly a single track route with lots of passing places and the requirement for pathing time to allow for passing trains in both directions. The line is busy nowadays as Trenitalia are also competing with Italo who run at least two services a day, plus regional services from Benevento to Caserta and Naples.
Once back on double track from Foggia to Bari, the non-tilt journey times are programmed only a couple of mins slower than ETR485 timings. And from Bari to Brindisi and Lecce , there are no tilt speed enhancements. But here again the future is non-tilt because Trenitalia are building a new route across the mountains from Napoli / Caserta to Foggia, and enhancing the rest of Foggia to Lecce for as much 200kph non-tilt as possible. So the future for tilt in - Italy is very much approaching the buffers too.
I'm not sure anyone in Europe expolited tilting trains for frequency and journey times as Virgin trains did on the WCML. But the Virgin XC part of it never really exploited tilt to the maximum, and in one way that is a shame. it would have been interesting to see what could have been possible using tilt on XC especially as it might possibly have improved speeds in Scotland Cornwall, and on the middle bit from Doncaster to Derby.
It probably never helped the cause that Voyagers only offered 6 degree tilt and that limited the potential speed improvements. And the fact that the market doesn't demand end-to end journey time reductions. London to Glasgow competed with the air market. Penzance to Aberdeen doesn't seem to. On XC, the emphasis is connecting the cities in the middle.
