Both effects are real and they land at different times. For the next seven years an acquisition by a system usually improves collection certainty, assuming the assignee is an entity with actual financial substance rather than a thinly capitalized affiliate. At expiration, a system that owns a nearby outpatient campus consolidates sites, and a leased suite six miles from its own building is the obvious one to drop. Systems also sublease or go dark while paying rent, which protects your income and destroys the building's marketability at the same time.
On the guarantee question, whether the original PC and the partner guarantees survive an assignment turns on the exact guarantee language and on how your state's law treats a guarantor's release, and that's a question for real estate counsel reading the actual document, not a forum answer. Two things commonly matter: whether the guarantee runs to the lease as it may be assigned or only to the named tenant, and whether the assignment provision contains an express release. Silence in the assignment clause does not mean the guarantee travels.
What you can do while they still need something: an acquisition triggers estoppel and consent paperwork, subordination requests, sometimes a request for extra parking or a signage change or an expansion. Every one of those is a negotiation, and that's when you ask for a parent guarantee, a lengthened term, or a right to relet the space if they go dark. Price your cooperation.
The policy layer sits under all of this. Payment treatment for services delivered in off-campus outpatient locations versus hospital campuses has been an active area of federal policy for years, and it directly affects whether a system wants your address on its billing. Ask your tenant which site designation they'd bill your building under after the deal.
