SPRINGFIELD — Local real estate agents say 2026 will be another seller’s market, with home prices continuing to increase, but not on the same level as years past. The median price for single family homes in the Pioneer Valley, which includes Franklin, Hampden and Hampshire counties, increased 7.7% to $374,950 in December, compared with $348,000 in December 2024, according to the Realtor Association of Pioneer Valley.