That worked out pretty well with the PS3, right? IIRC, 3.51 is the only firmware that's hackable on the PS3.
Edit: 3.55
Up to 3.55 you can just install CFW easily. You can downgrade some consoles to 3.55 using hardware. There are a few consoles that can have CFW installed using hardware without going to 3.55.
If you have metldr2 then you can't have CFW yet, there are people looking at it. There isn't much urgency because there are plenty of exploitable consoles, but a lot of them have started to die due to manufacturing issues.
People thought the DSi was unhackable when the save exploit bugs were fixed, but it's springing into life.
Predicting whether another hack will come or not is hard.