Different format, different bowling attack and fielding strategy. Besides, as far as I know the West Indian players are not having good time with the managements. So, I would not expect much from them. If this was T20 world cup then I would bet for them but in this one, I think they may even lose some matches against Bangladesh and Afghanistan if they manage any match with them (I have not looked at the fixer yet).
Honestly speaking, West Indians have some great players like you mentioned above but greatness needs management, team spirit, certain goals which the West Indies team do not have right now.
By the way, do you guys think Gayle is fit for 50 over matches?
Looking at his movements I doubt he is fit for long innings. He is okay to hit 6s and 4s in short format like T20 but for 50 over matches it will be too much to ask from him. Don't forget his back injury which all the bowlers use against him. There was a time when a blower bowled a body length ball then Gayle used to hit it hard but now, he can not do much and the bowlers use it in favour of them.