Just because Grodin's last known place to be was obliterated doesn't mean he's dead. Come on, this is scifi we're talking about.
There are as I see it so far 9 possibilities.
1. He's dead, he blew up - end of story - bit of angst
2. Someone helped him ascend - though I find that option a bit cheap and don't want to see it - rather have him dead than that be used.
The next 3 are based on what if the Wraith 'culled' the station - I admit its unlikely and I would have to look back and see if there is any evidence in the special effects in the scene to show any beaming off. But should that have happened I see three possible outcomes.
3. He's a tasty snack for them.
4. He ends up being experimented on much like the rumours for another character and appears in later seasons.
5. Considering the Wraith might know that Bob, their spy on Atlantis is dead, they might keep and interrogate Grodin. Obviously if he was kept on the hive ship and if those got destroyed in the seige then he's die there instead of where they all think he did, but if somehow he remained with the Wraith I could well see them using him to gain the advantage against humans, to learn of the technology etc once they realise the human threat is a bit more serious - all presuming that everyone on Atlantis wins the fight of course.
6. There was alifepod Grodin got to. He does know the systems well and maybe he looked it up and got to it in the nick of time - and it might have got missed in the explosion and debris. If it got hit by debris and he was unconscious then that would explain why he didn't radio to say he was still alive.
7. If the station had some odd portected thing like a lifepod - with everything but that core bit being obliterated and it just looking like a large enough part to be big bit of debris (there did seem to be some large chunks afterwards too)
8. Back to what if he found something on the schematics - maybe there's a transporter down to a base on that planet nearby. Hard to believe since they never mentioned anything Atlantean on the planet in The Defiant One, only that damaged Wraith ship.
9. Same as above, but maybe to another station like that or a different safe planet?
I know some are far fetched but I think they aren't all so. The one i'd most like to see done would be 5.
The rest of the episode...
Wish we could have seen the T-rex.
McKay was great, loved him as an astronaut and the gravity moment when Peter flicks the switch - plus the way his voice cracked up at the end when telling Elizabeth Peter was dead. :(
Yay for Zelenka getting to do stuff.
The database conundrum is a nice touch, good setup for problems in later seasons. Weird but cool to have the data as a casualty of war, or all the people they might not save for deleting something vital.
Obviously a teriffic/terrible cliffhanger but I liked it that way, on to the next part soon I hope.
plus Joe finally got to name a wraith Bob!