Cam had a pretty good year in 2015 (Rating 99.4 - QBR 67.0 - ANY/A 7.20) but really hasn't done anything exciting since...
2016 - 75.8 / 48.0 / 5.46 (15 games)
2017 - 80.7 / 53.3 / 5.28 (16)
2018 - 94.2 / 55.0 / 6.15 (14)
2019 - 71.0 / 24.6 / 5.09 (2)
2020 - 79.8 / 50.8 / 5.48 (10)
I don't see any real reason to believe he's really significantly better than what we've been seeing from him.
To put those numbers in context his Rating+ - ANY/A+ numbers (where 100 is average and higher is better) are
2015 115 / 115 (the good year)
2016 81 / 90
2017 88 / 88
2018 105 / 100
2019 72 / 85
2020 85 / 90
(Unfortunately PFR doesn't give QBR+ numbers but they wouldn't be massively different)
FWIW Brady's + numbers over the last five years
2016 133 / 138
2017 117 / 119
2018 110 / 115
2019 95 / 100
2020 104 / 105
So even Cam's high point year was only about the same Brady's 2017/2018 combined performance and nowhere close to any of Brady's best seasons.
Also FWIW there's a guy who will likely be available next year and who probably won't cost very much, who has actually performed pretty well in recent years despite having been messed about a lot on largely bad teams...
2015 98 / 104 (16 games)
2016 72 / 83 (14, 11 starts)
2017 95 / 102 (6, 3 starts)
2018 114 / 125 (8, 7 starts)
2019 92 / 94 (15, 13 starts)
2020 102 / 102 (8, 7 starts)
Furthermore this is a guy whose QBR does perhaps indicate some reason for optimism over those numbers since it has been pretty decent at 62.1 (2018), 66.6 (2019) and 73.8 (2020)
(For comparison Brady 66.6 / 54.5 / 69.7 and again Cam 55.0 / 24.6 / 50.8)
Now he's not going to be the QB of the future, but as a stopgap for a year or two while the Pats rebuild and try to find the next big thing? Maybe we should be thinking more about...