Microsoft doesn't lack resources, but it's a stupidly cheap company. If it doesn't think that it will get enough profit from Halo 2 Anniversary, then it won't get made. On the subject of matchmaking, it's expensive to maintain the necessary servers. Microsoft is, as I mentioned before, very cheap and greedy. They are unlikely to be willing to spend the money required, especially with Halo 4 coming out in just a few months and a rumored console release at the end of next year.