For one, looking at the lib_rtos_support which is a software library that provides support for running an RTOS on xCORE. Any RTOS. And libraries like lib_i2c are still in xC and unchanged for xcore.ai. With that in mind I would think that xTIMEcomposer would be as is, just adding the FreeRTOS library, to take portability one step up.
One the other hand, XMOS does not mention XC. Not in the initial info, and not now.
Mark Lippet says in  (in the context of Neuromorphic Computing) that
I hope, what he's saying is that in order to switch over to xcore.ai it's not necessary to learn any new language. xC is hidden below the bonnet. Task are supported by FreeRTOS. Not necessary does not mean, not possible(?)Lippett also said any technology that involves a change in the way people think about programming systems will be faced with challenges when it comes to market. Even the Xcore, though based on a RISC architecture, faced market challenges. Lippett said any technology that involves new programming paradigms will meet resistance.
“The key observation that we’ve made is you really need to be very close to a pre-existing, familiar programming model in order for rapid adoption to take place. So, I think that’s the challenge, to make the benefits of those technologies available from a cost perspective, but also accessible to the skills of the existing community, otherwise adoption will be very slow,” he added.
“I’m comfortable that we’re not competing [with neuromorphic computing] in the very near term, but clearly it’s an exciting technology and one to watch.”
Also, in  XMOS does not mention neither the xTIMEcomposer or XC. Null. Zero.
I have tried to ask around, but silence has prevailed.
Now, could anybody from XMOS lift the veil?
 XMOS FreeRTOS port (disclaimer: no money, no ads, no gift, just fun and expenses)
 Will Neuromorphic Computing Compete with Today’s AI Accelerators? by Sally Ward-Foxton in EETimes, see https://www.eetimes.com/will-neuromorph ... elerators/ (13Apr2020)
 XCORE.AI product brief, marketing material by XMOS, see https://www.xcore.ai/wp-content/uploads ... Brief.pdf (2020)