PB
No.
'es' is 2nd person singular (present, indicative, active) it can only mean "you are."
Tomorrow (Cras) is only an adverb; never a noun in Latin.
'Cras es noster' means "tomorrow you are ours."
If you want the say "Tomorrow is ours.", that is, "The future is ours.", you can do it one of two ways:
Futura nostra sunt.
Futurum nostrum est.
…you can change the positions of the words any way you want within the sentence; the meaning will remain exactly the same.