Guild Wars 2

Old weapons too will be useful with elite specs ? for example mesmers will be chronomancers , mesmers should use shield for elite specs ?

They can, but they don’t have to. The old weapons are still available, but the new weapon seems to “fit” best with the new elite specs.

I think there’s people which don’t want change weapon , like me. Im thief player , I think d/d is best looking weapon for thiefs and I don’t think change weapon , with new meta I will be weak ?

We can’t say that now, we don’t have any infos on the thief elite spec.
It is possible that this spec is so overpowered that it will replace every “normal” thief, but it is more likely that it is just an alternative you don’t have to use.

If new specs comes to f2 , f3 or f4 , utilities and elite skill but don’t main or off hand , this will be very good , new weapon should be option from usable weapons