No, this would be an incorrect way to categorize. Not all Sea Islands are GCN 1.1 (which is a fake naming convention anyway).
Shifty has the right summary of what's been going on. Ideally when the R300 series is revealed, someone can check the Pitcairn cards to see if t they have Tier 2 Tiled resources, that would imply that family is irrelevant to categorizing D3D feature levels as well. If family is important, the table provided would showcase which families support which feature levels.
but as the table stands, family appears to be important - if we follow this trend then we should be able to anticipate the 300 series GPUs as well.
Radeon , 7850, 7870, 7970 and 280X is pitcairn (feature level 11_1) (this aligns well with PS4)
But 7790 and 260(x) is Bonaire (FL 12_0) (this aligns well with Xbox)
285X - tonga (FL12_0)
290 - hawaii (Fl12_0)