I'm surprised how few people actually understand the letter from a Chinese cultural perspective. Clearly, they give Core a deadline in a face saving way. Superficially, the letter looks like support to Core, while embedded, there's a diktat to include a HF in their roadmap with a deadline of three weeks.

3. In the next 3 weeks, we need the Bitcoin Core developers to work with us and clarify the roadmap with respect to a future hard-fork which includes an increase of the block size. Currently we are in discussions to determine the next best steps. We are as a matter of principle against unduly rushed or controversial hard-forks irrespective of the team proposing and we will not run such code on production systems nor mine any block from that hard-fork. We urge everyone to act rationally and hold off on making any decision to run a contentious hard-fork (Classic/XT or any other).

This is where shit gets real. This is extremely strong language, they specify not only the timescale (3 weeks) but also explicitly state the subject matter (with respect to a future hard-fork which includes an increase of the block size). This could not be any clearer. They want a blocksize and they want a concrete commitment from core within 3 weeks of when that is going to happen. The implications here are twofold, that the timescale had better be satisfactory, and that failure to provide a satisfactory timescale carries and unwritten 'or else' clause "We need" is the key phrase here. Very strong language from the east imho.