There's lots more work to be done - 150s, 153/155s, 156s all have to go and soon. The 465 and 466s are likely to be replaced with new EMUs in the new Southeastern franchise, and the 165/166s aren't going to last forever, they could potentially be replaced by the end of the next decade - technically speaking they too are already end of life, but in the context of sprinters they seem nowhere near it. The DMUs on southwestern will probably be replace by the end of the 2020s as well, as could be some of the other 158s around. Then there's the EMT HSTs to replace, as well as long-term considerations for what replaces the 'stopgap' converted HSTs other operators are using. Plenty of work around, the question is who will be getting it?
There is a fair amount of work, but you've also got to remember when that work will be required. The next 5 franchises to be awarded are South Eastern, West Coast, East Midlands, Cross Country, and Great Western, which takes you up to the start of 2020 and will have a few orders as a result - Hitachi or Alstom for SE metro stock replacement (854 vehicles), HS2 stock and potential voyager replacement (100 vehicles) for WCP, potential full fleet for East Midlands (~60 regional vehicles + ~280 HS vehicles), GWR potentially going for replacement of all non-new stock (~400 vehicles) and say another extra ~100 vehicles for XC.
854 metro vehicles, 479 HS vehicles, and 424 DMUs. Assuming that the metro vehicles all go to Hitachi N.A., that's a solid 2 years work at maximum production of 35 vehicles/month. The HS vehicles would keep Litchurch lane ticking over for a year or two (big "if" that they get that work though), and the DMUs would probably keep Newport going for a couple of years as well. So that's 3 plants ticking over until around 2023 in something of a "best case" - it's entirely plausible that Litchurch Lane get no orders for the forseeable and run out of things to build after 2021, or that Alstom pick up the SE Metro contract leaving Hitachi with a handful of AT300s
After that, the
franchise schedule looks unhelpful, there are potential orders from Chiltern & 313/365 replacement for TSGN at the tail end of 2021, but then the next realistic chance of orders would be 15x replacement on SWR with the next franchise commencing mid 2024, and Northern which is going to be the next big order (you'd hope!) in 2025. Certainly there don't seem to be any potential guaranteed wins (commuter EMUs) for Bombardier other than TSGN in the current franchise schedule, they need to hope that they pick up some orders for the HS Aventra, and potentially develop a turbostar replacement as well if they want a better chance of staying open