depends what you are making.

A five colour palette for artictic models could be good.

For practical uses, yeah 2 or three different materials would probably be the most you;d use.

But bear in mind it's 5 different 'toolheads' not just plastic extruers.

You could add a chocolate or paste extruder or even a milling head.

And no doubt once the machine is in full production a whole bunch of different toolheads will be coming onto the market as well.

There will definitely be a laser head, which works well with 'wood' pla.
Or simply for putting nice clean and tiny holes in things for wire armatures.

A multi extruder setup is limited to filament - but th way this system works - lots and lots of really cool options. :-)