In proposed Companies bill 2008, clause 17 actually says that if there is any alteration in memorandum and article of the company which are identical like change of registered office and change in name etc. then to register these change company may re-register itself with ROC because under clause 17 it is clearly mentioned that a company may re-register itself by alteratin of MOA & AOA (also refer Clause 12 & 13 of companies bill,2008).
To conclude it is not clearly mention that re-registration is mandatary in that case.