MacArthur was SOOOOOOOOOOO much better than Lombardi last season, looking to dump MacArthur and give his spot to Lombardi makes absolutely no sense to me. MacArthur is 3 years younger, hasn't suffered a major concussion, and is better than Lombardi in literally every way except pure speed.
Lombardi is 30, and turns 31 in two and a half months. He suffered a major concussion that caused him to miss an entire year of hockey, and he really showed no improvement from the start of last season to the end of last season. I don't see a reason to expect him to bounce back in a major way, and IMO he was the worst regular forward on the Leafs last year. I'd much rather just let him go, and let young guys from the Marlies battle for the spot he frees up.
I'll repeat again that I really think Lombardi will have trouble getting another contract anywhere in the NHL next offseason. He's small, soft, and not very effective with the puck, he doesn't bring much to the table other than speed at this point in his career. I can easily see him having to sign in Europe or the AHL.