then hor, what would be a polite sign off huh ? ....
like, we hope to hear from you soon, we hope to be able to work
with you in the future etc ? ... 
Errr...that depends on your relationship and the stage of this
business negotiation.
Hear from you soon, is kinda means you are still offering and
its not a done deal.
Hope to be able to work with you in the future. Kinda
means you are not going forward with this deal.