Could mastercoin be used to issue/trade shares in IPOs?
Would that mean that a place like btct.co and havelock Investment would be made somewhat redundant?
This is a grey area. Yes a coin could be issued that tracks the value of a share on some exchange. Issuing shares are another matter all together. It is technologically possible to have "real" assets owned by a derivative coin of mastercoin but trust and law come into play.
I'm certain Mastercoin protocol can evolve to include features no one has even thought of yet including real assets.