I don't think that the gods will die, but may be a bit more distant than they have been in the past -- assuming these changes happen.
Many of the good drow could have been destroyed, but some coulld exist as remnants. Drizzt may learn of some and seek them out and bring them to the safety of the Silver Marches. (Never assume a character who narrates events know everything.)
One alternative for the merging of two worlds would be if someone opened up gates and ended up merging parts of another world with the Realms and possibly some locales changing places. This would be more than enough to create a lot of chaos. (This may also create theological turmoil if the new people to the Realms brought in their own deities. It might take a long time for some of the gods of the Realms to adjust and their may be a reluctance to interfere directly after so much damage.0
(Possible narrative from someone besides Drizzt, in this case, imagine an eladrin wizard narrating. Okay, just doing this for our amusement as we know that WotC will be using some real world mythology and legends to draw on.)
"Sadly, Netheril was not the only place which attempted magic that was beyond their power or control. The war between Thay and Mulhorand reached its peak in an attack that Mulhorand thought that they could counter. However, it was not enough, and the magics blended in a horrifying way, devastating parts of both lands. The Mulhorandi called on their gods, and their gods answered."
"The devastation spread like a wave, opening up rifts between Toril and another world. Villages and cities vanished to be replaced by forests, swamp or even cities from tht world. Or villages and cities were utterly destroyed as parts of that world fell on them. The inhabitants of that world were utterly confused as they found themselves in a strange and shattered land called Faerun. Strange horrors disturbed the Underdark, leading many to flee -- to the surface."
"The gods of the newcomers also apparently heeded their prayers, and many voices were raised in supplication and fear. I remember, a tribe of Uthgardt barbarians were battling giants that had appeared in a village. A tribe of the newcomers saw the battle and a paladin of Tyr called out his god's name. Some of the warriors of this tribe shouted the name Tyr and other strange gods besides, and joined the battle and a village was saved. That was one of the few days of joy in many years of pain."
"Now, the gods seem reluctant to intervene, perhaps fearing that their mighty hands might damage a wounded world. Still, I have seen those who have called on their faith to aid them, and some have journeyed from afar to help Toril in its time of need. To quote an old friend dead many years, 'They have their work cut out for them.' "
"Cormanthor was hit heavily, and the followers of Ellistrae were slain or fled. Some still live, in hiding or hiding their faith. May they endure. May those islands of civilization and peace that remain endure amid a rising sea of perils."
"Faerun has been through much this century. Some heroes fell, sacrificing their lives so th at others could live, and new ones emerged. Yet, at this time, the world is still in need of heroes. Whether you and those dear to you are native to Toril, or are among those who came here in an age of sorrow, the world has need of you. May it be said that you proved worthy of the challenge of our age. The choice is yours: to seek to save or damn Toril or to follow your own path. Choose wisely, as the world is watching."
(Okay, incredibly corny, but hopefully someone might like it.)
One thing I would like to see in the Realms are examples of characters from different classes, perhaps even a few who interact as an adventuring party or allies.
