First, I would like to welcome you to the forum. Now, on to your points.
1) They are likely to lose 4+ Senate seats again.
Perhaps, but this is wishful thinking on your part. Don't forget the Christ Dodd, Michael Bennett, Harry Reid, and Roland Burris are all vulnurable, and the political climate
may be more favorable to Republicans.
2) The governor races will likely put Democrats in charge of big and growing states (CA, FL, AZ, NV) and the GOP in charge of less-populated ones (WY, KS, TN, OK).
I am not familiar with the specific candidates in these states, but I think the GOP stands a chance in the four you mentioned.
3) Redistricting is coming up immediately afterward.
Indeed.
4) Although red states are trending toward greater numbers of congressional seats, this trend is likely to be drowned by greater demographic changes-- increases in Hispanic and Asian populations as well as the continuing rise of younger (more liberal) generations into the voting ranks.
Yes, but keep in mind that Hispanics, Asians, and the young are not shoe-ins for the Democrats. Tone down the immigration rhetoric, you are competitive with Hispanics. Don't emphasize the social issues and instead focus on small government, fiscal restraint, and lower taxes, and you can win the youth as well as the Asians. I forget where, but I saw a poll where, in terms of economic issues, the young were divided about the same as the older voters. What cost the Republicans was the war in Iraq and social issues, which won't be on the forefront in the 2010 election. You and other Democrats should stop make assumptions about demographics, or it could cost your party.
5) The Democrats have clearly established their party as the big tent, while Republicans continue to commit fratricide toward centrists, despite all evidence suggesting this is poor strategy.
The GOP is turning around. Mike Castle and Charlie Crist are possible/current contenders for the senate that are moderate. I think they will have more moderates than in 2008.
