If as a promotional engine, we could do that for those not currently logged in to the Steemit interface but I think that can also backfire and could lead to people calling Steem a scam if it they visit again in 5 days and then it has crashed.
Remember that not everyone is crypto-knowledgeable.
while this is possible if SBD prices normalize (it usually takes quite a while), it's certainly also true that currently your posts are worth 5x more than the advertised amount
It is also true, and very real, that posts made 7 days ago are getting 5x the advertised amount at payout right now. And you can't ever do that justice without at least risking over advertising the amount you'll get in the future.
Current price is still the most accurate indicator of actual price. Yes when it's high if you start writing now you'll likely get less in 7 days, but when it's low, there's a chance your posts will be much higher in 7 days. On balance, displaying the value in USD is still the most honest and beneficial way.
Right now we're missing an opportunity to attract more people onto the platform as overall the payouts are actually 5x what they currently have shown.