SSL 4 and below last year and within last 3 years will surely be applied. But this only caught around 1K last year. Surely they will cast a wider net for ISP.
The invitation-only VSP in 2012 was for all with SSL 3 or below for past 3 years but I don't know how big a pool that opened up.
Enhanced retirement based on past offerings is likely to be open to all eligible by 75/55/65 rules or those very close and the offering is likely to be severance and medical coverage till actual retirement.
I suspect combination of SSL and time in grade will be used to net more ISP candidates since this is also likely to get their favorite demographic of older white males.