Depends on your definitions.
"entrepreneurs who have had an exit in 2012, and little to no income before that" -- Pretty narrow.
"People expecting fair treatment from their fellow citizens" -- Not narrow at all.
Retroactive law of any kind sucks. As the point of law is to provide rules to guide conduct, "retroactive law" is something of a semantic nullity -- it cannot possibly guide behavior because its guidance is not knowable as people behave. It is little more than than infliction of a legislature on some population, under the color but not the substance of law.
Your freedom and property depend on our general refusal to apply such law to you, no matter how much we may want to. Absent that general refusal, you depend on your absence from sets any set of people from which we might want to apply such law.
If you are confident that you will be the same as everyone else on all important dimensions, you should be safe without that general refusal. If you've any ambition to be different in any important way, maybe you should consider your interests more broadly.