This is an easy one. If his performance has decresed over the last 2 years. Don't offer arbitration. Congrats you got the best years of a pitcher's career without overpaying.
Best case scenario: He gets pitches to a mid 3 ERA for the next 3 years
Worst case scenario: His arm blows out in spring training
I'm betting somewhere inbetween. Why lock up a guy for 3 years when in 2013 they are supposedly going to be ready to contend and may need to add that last peice?
The only long term contract I see Wandy getting is a 3 yr 30 with the 3rd year being a 2 million buyout option. Maybe even a vesting option with innings pitched. He's had 2 good yet streaky seasons. It makes no sense to lock up a guy for 3 years when nothng about his past performace says he close to a sure thing.
That's missing the point on arbitration. If his performance drops to the upper 3 ERA range, he's still going to get a raise in arbitration. So, if he keeps performing, you're going to be on the hook for more every season. If he's someone the club wants around in '13 and they think he'll still be good, the cheapest way is to avoid going year to year. Unless he falls off the map, he'd be a valuable piece to any club at that point.
If he'd go for a 2-year deal with an option for the 3rd year, that's fine. That's what Myers got, though he's had a wildly more inconsistent career than Wandy. The club wants to do some kind of multi-year deal, maybe that's what they have in mind.
I don't get all the streaky talk. It's not uncommon for pitchers to have one or two off months per season, even very good pitchers. Cliff Lee has them, Sabathia, Oswalt, etc. If a guy doesn't have an ERA in the mid 2's (or 5+), chances are he had at least one month where his ERA spiked. Maybe it was one or two bad starts (Wandy's usual m.o.), maybe it was a few starts where he gave up 4 runs. But, that's the way it usually works.