Well, I know it would be a herculean task to convert TiTS to HTML5, but I also think it would be good for the devs to share a single codebase for CoC2 and TiTS.
Specially because flash's horizon will probably come waaaaay before TiTS development is finished, and I think it would be a huge quality of life improvement for the devs to maintain a single codebase for engine stuff instead of maintaining 2 whole engines.
Of couse CoC2 is still very early into development and would not make sense to start the transition now, but I think it does make sense in the long run once CoC2 matures a bit more.