First ask yourself is Cobol good for what it's used for and is switching to another language "better". A lot of languages are created for a specific purpose and when something better comes along, that's when you should probably phase it out. Switching to another language so I can get a cheap / inexperienced programmer who will likely make a huge mess of it is not a good idea.
Second, anyone who calls themselves a reasonable programmer should be able to adopt another language. It might take them sometime to become efficient or skilled at it but the point is a good programmer should be able to pick it up. I remember in my final year of university we got exposure to some downright weird or difficult to program languages like LISP and we were still able to make do.
Third, ignoring the issue is the equivalent of saying "Screw it!" and kicking the bucket down the road making it someone else's problem. This is never a good solution, have a phase out plan, train some employees or a fallback. Don't just wait till your last skilled programmer retires and you're now up the creek without a paddle.