The lease on the Royal Lodge was intended to outlive Andrew. While downsizing certainly makes sense, I think a key variable is if one or both of his daughters are interested in the property and are willing and able to meet the terms of the lease.
While the bulk of her estate went to Charles, I am willing to bet that HLM left hefty bequests to her three other children where, even after taxes, they have enough to maintain their lifestyles for the rest of their lives.
What I am trying to figure out is was Andrew's income as a working royal all that substantial, and can that income be replaced? My understanding / recollection is that the monarch and Prince of Wales get funding from their respective duchies, the remaining working royals get funding for their royal work and a personal allowance from their respective patron. Andrew reportedly received an allowance of £249,000 from his mother. While that is not chump change, I suspect that there are discreet endeavors that Andrew can engage in to replace his allowance. One thought that crossed my mind is that the Royal Lodge, in and of itself, can be a source of income. My understanding is that Prince Edward is allowed to generate income from Bagshot Park, I wonder if the same is true with The Royal Lodge? Could Andrew aand his family, for example, host shooting parties or other events at the Royal Lodge?
Again, as noted above, if Andrew wants to downsize, that is understandable, especially if his daughters have no interest in the Royal Lodge, but if the Yorks want to keep the Royal Lodge for the remainder of the lease, I don't see that as unworkable, assuming that they have the competency to do so.