Assombalonga moved to London Road from Watford last summer with Posh paying a club record fee - eclipsing the £1.1million handed to Crawley for Tyrone Barnett in 2012.
He scored his 33rd and final goal of the campaign last weekend in the first leg of the League One play-off semi-final against Leyton Orient, who on Tuesday night defeated Peterborough to reach the final at Wembley.
The 21-year-old's exploits have reportedly made him a target this summer for several Championship clubs this summer.
Ferguson said: "Britt has scored a lot of goals and it's a fantastic achievement for the boy. However, he's got lots to learn and lots to improve on. But you can't take away the fact he's scored so many goals."
Comparisons have been drawn between Assombalonga and Dwight Gayle, who left Posh last summer for Crystal Palace in a deal thought to be worth in the region of £6million.
Gayle scored seven Premier League goals this season including four in the final two games of the season against Liverpool and Fulham.
Ferguson added: "It's an easy comparison to make but the difference is Dwight did it in the league above, in the Championship, so we'll have to wait and see.
"Hopefully if we get in the Championship that will be Britt's test. But we've done it with others, (Craig) Mackail-Smith, (Aaron) Mclean, Gayle, (George) Boyd and (Lee) Tomlin, we moved them on and we managed to get another one in. It's becoming more difficult but the boy knows where the goal is."