I've been upgrade eligible since Monday at 2pm. I have two in the uppers and two in lowers (trying to get all four back together in 401 or 454) so I've been able to see all 100-level and 400-level seats for upgraders. There were never any upper deck options as good as the new ticket holder options I saw on Memorial Day when there were open seats in Section 401 Row 2 and Section 454 Row 3.
There were quite a few options on Monday in 401 for upgrades but they were mostly rows in the low teens. At the moment, when I look at my season ticket account for upgrades there are:
Three together in 401 Row 10 (which I think just opened up) and three together in 401 Row 12.
Two together in 402 Row 9
Two together in Section 427 Row 11
No open seats at all in 454, 428 or 429 (at least not up to Row 16 which is highest I can see).
4 singles in 104, 1 single in 124, 3 singles in 125, 5 singles in 139, 1 single in 140
No pairs in the lower sidelines
When I log out of my season ticket account and follow the link in the new season ticket holders email from Memorial Day, I see different options that don't appear for upgraders.
Six together in Section 401 Row 14 and a single in Row 12
Two together in Section 402 Row 14
Sixteen available in Section 427 Rows 13-15 (mostly in twos and threes)
Twenty-four available in Section 428 Rows 9-15
Single in 454 Row 15
Eight in 453 Rows 13-15
Twelve in 117 (mostly pairs)
Twelve in 126 (mostly pairs/three)
Five in 138 (all singles)
Three in 105 (all singles)
So unless I am missing something, the ticket office is definitely holding aside a completely different set of inventory for new ticket buyers than for upgrading season ticket holders. At least some of the options for new buyers still look better than those for existing ticket holders.
Draw your own conclusions...