The company Cutting Edge Bullets is developing heavy weight bullets for the ever popular .22LR. They report having a 30, 40 and 50gr bullet loads for the rimfire. Of course these will require faster twists rates for the barrels except for the 30 grain load.
Lilja Barrels has announced they will be doing a limited run of 1/9 twist barrels to work with these new bullets.
With these lengths we will be mainly looking at single shot bolt action rifles until a lot more detail gets worked out.