Well the problem with the current model is that they are printing more Steem Dollars. So naturally that will eventually lower the price. You can't have a currency that goes up forever that would make it useless. Also you have developers that is being paid in Steem Dollars and their salary is hard to calculate if the SBD fluctuate too much! Remember that the high SBD has only been lasting for around 2 months. So it will probably come back down again to it's natural level!

As @exyle said in the video the good thing if it comes down is you will have less competition on the platform because less will blog! So it's actually a good thing for the opportunist! Remember that Smart Media Tokens will be launched soon so if you invest in Steem you may make a massive profit if you hold it! But you have to be patient! And as with all things in life it's a risk and may not succeed. But there is a good chance it will increase in value!