Looking at the trail map, here's my best guess at the 26 trails that will be open:
1. Strawberry Hill
2. Pioneer Glade
6. Honeysuckle (around the world)
8. High Five
10. Return Trail
11. Bambi Glade
13. Upper totemoff
14. Lower totemoff
16. Whitefeather Gully
17. Upper Powderhorn
18. Powderhorn Bowl
19. Powderhorn Gully
That's all the green/blue terrain that could be open. There are several possibilities under lifts 4 & 8 which could open even though the lifts won't be running, but let's assume that they'll keep those closed until their respective lifts do start to run.
That leaves 7 more trails that will definitely be open. Here's my best guess:
20. Zagava (usually the first black to open)
21. Al's Run
23. Walkyries Bowl
26. Lower Inferno (as Al's will be closed at the halfway point as usual during the early season)
There's my best guess! And then on top of that, the additional terrain that will open "as conditions allow."
Note: I did not take acreage into account for this guess at all. There will be 400 acres open if that helps anyone make a better guess.