I don't think anyone will be able to advise you on what the Client may do. From a contractual point of view, your offer is no longer valid if it was fixed for 120 days. You would therefore be entitled to bring this to the attention of the Client and propose a negotiated adjustment. You would have to do this before starting any work. Under procurement regulations, the Client would have to request all tenderers to advise of adjustments to their tenders to take account of the delayed start. The Client could also stop the process and start again (or not).
I suggest that you should check what rules the Client set in its IFT in respect of tender validity to ensure your 120 day period is not against those requirements. I would also check that the standard wording in respect of the Client not be bound to accept any tender are included - they will be.