Personally, I think its already happening. My PBN based stuff from mid to late 2017 is not behaving anything like my stuff did back in 2016. This is from Google back in December 2016 and he explains how they would counter them.
ha hi man, you get around these forums! Yeah I think you might be onto something there. Paid guest posting is going to become the number one strategy then in the near future!
Problem for Google is how do they know what is a re-used domain used just for link collection and what is a domain registered by a new owner without any knowledge that it has a "drop" history.
Yes, we can not expect link juice form the expired domain. The backlinks also be wasted after expiring the domain.
I think it depends on what you do with the expired domain. If you recreate the website to its original state or at least keep it in the same niche, the backlinks will stay relevant