The only reason the team would be exploring voiding the contract is because they ultimately don't think he'll be any good when he comes back, or his personal situation will negatively affect his performance or the team and they don't want to risk him being a toxic asset. Whatever they know or think they know is informing that decision.
In any case, they can't live with the uncertainty that the lack of communication is causing. Rodriguez being gone and not keeping the team updated affects all sorts of things with the team, including planning the use of minor league arms to replace him, signing of free agents, draft plans, 40-man roster management, and just budgeting for his salary. If he ever decides he's ready to return, the team would have a hard time justifying keeping him on the restricted list, so they'd have to start paying him whether or not he returns to the roster. The team cannot tolerate 5 years of uncertainty over all of that if he ultimately never returns.