100-Year Starship some way off

I've heard of this, the link below indicates someone calculated when we 'should' leave by and came up with 1,100 years from now to travel to Bernard's star. (6 light years away)
http://en.wikipedia.org/wiki/Wait_Calculation

Of course I wonder if they are considering a few things. First if you are leaving with a full industrial base, any further advances in propulsion could be transmitted to the 'lead' ship. Second unmanned probes would need far far less mass and I wonder how this would affect the calculation. And lastly unlike say a 15th century ship at sea on the atlantic vs. a 747, if you are leaving with a home/community it's more like taking Hawaii and pushing off to be on your own. So how much do you care when, as has been said, you have everyone and pretty much everything you need.
Brooks

--- In spacesettlers@yahoogroups.com, "William" wrote: