Joining a massive project like this will force Canadian astronomers to make some painful choices. I mean, it's great to have this sort of problem but that does not mean that the sting will be less. And yes, lets be honest - the costs will probably rise, at least because we don't know what our share of the operating costs will be (IIRC, the rule of thumb is 10% of capital costs, so about $25M annually for Canada's share). And then there is Canada's involvement in the Square Kilometre Array that will need to be sorted out - a project that will cost at least as much as the TMT (but for which there will be no competing telescopes - it's all or nothing).
Yeah - expect to hear more.