Titan it's still  an excellent card.
You can still get Titan on ebay for around $650-700, as a matter of fact my nephew just picked 1 up for $750 in almost new condition to sli with his older 1 I sold him last year.
 

I went from 2x TitanBlack:SC to 2x 980:SC and got very little performance boost @ 1440p.  I wanted less heat in the 10'x12' man-cave and it was worth it for that reason. I wouldn't call a 980 over Titan a true upgrade, specially at higher resolutions.

When to upgrade will be up to you, sorry to say.  Some folks will upgrade as soon as new hardware comes, as soon as new games come; and there isn't a break (unless one competitor is lagging new generation, which ironically allowed for Titan's existence in the first place).
 
I say stick to your price bracket, nVidia created Titan to give professional level products to the masses while AMD took their time to actually have something better than GTX680; in the meantime their new GTX980 is faster than Titan Black at half the price, still waiting for AMD to come up with something better than R9-290X.  No doubt nVidia will succeed the Titan Black with another powerful $999 item to justify paying so much for it.  
 
If you either can't wait or don't want to spend so much, then GTX980 is your option; but I suggest you wait as Titan Black's successor will be worth it, we just don't know when it's coming.  It has to be soon; there is a rumor AMD will have something marginally faster than GTX980 so far codenamed "Fiji", won't make Titan Black sales any better and nVidia has to do something.  
 
It could be called Titan-X, or may not be branded as "Titan", definitely will not be part of the GTX900 series if it is priced $999+ for a single GPU.

lehpron
When to upgrade will be up to you, sorry to say.  Some folks will upgrade as soon as new hardware comes, as soon as new games come; and there isn't a break (unless one competitor is lagging new generation, which ironically allowed for Titan's existence in the first place).
 
I say stick to your price bracket, nVidia created Titan to give professional level products to the masses while AMD took their time to actually have something better than GTX680; in the meantime their new GTX980 is faster than Titan Black at half the price, still waiting for AMD to come up with something better than R9-290X.  No doubt nVidia will succeed the Titan Black with another powerful $999 item to justify paying so much for it.  
 
If you either can't wait or don't want to spend so much, then GTX980 is your option; but I suggest you wait as Titan Black's successor will be worth it, we just don't know when it's coming.  It has to be soon; there is a rumor AMD will have something marginally faster than GTX980 so far codenamed "Fiji", won't make Titan Black sales any better and nVidia has to do something.  
 
It could be called Titan-X, or may not be branded as "Titan", definitely will not be part of the GTX900 series if it is priced $999+ for a single GPU.

yes there will be a new Titan it will be coming with the new 980's probably anytime next year from jan to april the difference will be the die size since NVidia didn't meet their expectations with the initial Maxwell release on just size. So yup lephron is right we are going to be seeing a new $999 card that will be the Titan Blacks successor in a Maxwell flavor.