No the sum is correct.

But Andy noted the use of a single transistor.

And as soon as you have a 1:5 or 1:7 (1:8 with dot) multiplexing factor, you require quite few transistors - or a single bus driver chip.

Switching to another processor isn't immediately an advantage. Yes, many of them can source current. But that does not imply that they can source more current than the traditional 8051 can sink current.

Going for many 7-segment digits, it's normally best to use external source and/or sink options. Especially since cost and board space requirements are quite small.