Typically a kitchen remodel estimate should take no longer than 3 days. We let our clients know when they should expect to receive their estimate after the walk through.
In your scenario, as stated by others already, the contractor may either be:
A.) not interested in the job - factors influencing this decision are primarily budget, scope of work, start time, and the amount of jobsites they currently maintain.
B.) they may have simply forgotten. We recommend sending them an email or giving them a call. Worst case scenario they will at least let you know that they are no longer interested in the job.