We haven't even started the first flights out of DEN yet, so for anyone to answer your question they would be guessing as well as you could. I would look to see how many flights the other carriers fly to/from DEN/PDX or DEN/SEA. If there are a lot, it must be a money maker with above average fares, so expect us to jump in within a year or two.
Should be able to connect thru LAS immediately. If only a nonstop will do, probably have a year or two to wait. If a direct (same plane) will do, you'll probably have that at least as soon as OAK-DEN kicks in, which may be quicker, like maybe a year or maybe less.