I believe Devils have always offered "pro-rata" season tickets. Well... definitely the last couple of years anyway. I bought 2 for me and the misses after Christmas for the remaining home games last season (Jan-Mar 2010). They sell them at the "season ticket price per game" if that makes any sense. Basically you save a few quid compared to buying seperately and you get a guarenteed seat for the rest of the season.
If I wasn't already a season ticket holder and intended on coming to the remaining home games, I'd definitely get one as we should be looking at sell outs if we're still challenging for title with a few games left - guarentee yourself a seat!
Just contact the Devils office, they'll send you a form to get contact details / see what seat you want / payment - send it back - you get a season ticket. Or even easier - visit the office.
This should be more widely advertised though as I suspect there's quite a few potential new season ticket holders who would take up the offer.