Do you think there will be a third world war?

Nuclear war, even limited tactical nuclear conflict, is extremely unlikely. Realistically and despite any saber-rattling, none of the major powers are maintaining any more than a minimum credible deterrence anymore.
And the minor nuclear states wouldn't have anything to do with their arsenals. Even if they tried to do something, I'm pretty sure they'd suddenly find they have a lot of bomb craters where their arsenals used to be.

We are likely to see new and so-far unconsidered forms of warfare emerge, including true cyber-warfare (not media scaremongering) and new forms of economic warfare.

Some form of outer-space warfare may also be coming later in the century. Control of orbit has too many MAD-like issues when the potential for Kessler syndrome is considered. But control of near-earth resources is a reasonable source of potential material conflict.

All this being said, I DO NOT think any of the above could result in a full-fledged world war.