A regeneration control system for an exhaust filter in an internal combustion engine system includes a first sensing mechanism for monitoring an exhaust flow resistance of the exhaust filter, and a second sensing mechanism for monitoring an attenuation of electromagnetic energy transmitted through the exhaust filter. The regeneration control system further includes an electronic controller coupled with the sensing mechanisms and configured to output a filter regeneration command responsive to an amount of particulate matter trapped within the exhaust filter. The electronic controller is further configured to weight data from the first and second sensing mechanisms in determining the amount of particulate matter. Weighting of the data may be responsive to an operating state of the internal combustion engine system. Related methodology is also disclosed.