A beneficiary in a will is entitled to see only the portion of the will pertaining to them. If your husband doesn't ask to see this, then there are three different scenarios:
1. He HAS been left something, and in due course of administration of the estate, the executor will inform him, but it may be a couple of months- up to a year( where the executor is doing his job properly, it shouldn't take more than a year).
2. He HASN'T been left something, in which case he is not involved at all and will have no entitlement to be told anything. If this is the case, when the will is probated it becomes a public document and he can obtain a copy from the local probate office for a small fee- again this could take a year or more.
3. There is no will, and his mothers estate falls to be divided on intestacy although this is unlikely given that the word 'executor' is mentioned. However if this were the case then your husband would certainly be entitled to at least a share of the estate and again would no doubt be informed in due course.
If your husband has not been left anything, and he feels he has some entitlement, then he should consult a solicitor. I have to say, though, that children do not automatically have any entitlement to a share in their parents estate unless they have not been adequately provided for in their lifetime ( usually where a child suffers from a disability or such like), or unless they had some promise from their parent of an inheritance which they relied on to their detriment etc. Really if he feels he should get something it would be worth his while to make an appointment with an independant solicitor for a private consultation about his possible ( if any ) entitlement and that should be done straight away.