ESA Decisions are taking 4-6 weeks but there are considerable delays in the Assessment process, if this is a new claim then I would expect you to be seen quickly, maybe 4-8 weeks but if this is a reassessment then it could be months before an appointment is booked.
The DWP may decide that an assessment is not required but it is extremely rare for this to happen.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems