Most things cannot be distributed as Blu Ray only, not for a long while so real question for less than Hollywood releases is how long will it be before we can afford to do both.
The question of shooting HDV vs DV is more complicated than most consider. There is more to it then just quality. Going to HDV will add a lot of time to your workflow, can your projects/fees warrant this extra time? When you deliver in SD are you looking for still in 16:9 or do you need to reconform to 4:3, if you do it adds even more time to your workflow.
There are a few areas that make working (shooting) in HD more demanding. You need more light than DV, you need better lighting and you need more precise focusing. The lack of attention to these details will hurt a HD project.
My rule of thumb is never by anything for something that you maybe doing down the road because by the time you get down the road there will probably be better stuff for less money.
If you do want to take the plunge into HDV my one recommendation is to build an edit system that takes the footage out of HDV on ingesting. That way you are not editing in the HDV codec.