can my ex-wife be engaged to another man while his divorce to his soon-to-be ex-wife has not been final yet?

They can be engaged, they just can't get married until his divorce is final, because that would be bigamy.  Being engaged to a married person is tacky, but it's not illegal. This answer is given in accordance with the laws of Virginia and may not be applicable in any other state.  It should not be construed as legal advice, as that would require a more thorough analysis of all of the facts involved in a specific case.  If you need further information or assistance, please feel free to contact my office for a consultation. Case results depend upon a variety of factors unique to each case. Case results do not guarantee or predict a similar result in any future case.