S&P 500: 50%
Wilshire: 25%
International: 15%
Bond: 10%

Just some comments.

I believe that about 70% of the Wilshire 5000 Index is made up by the S&P 500, so there is plenty of duplication here. My own preference would be to just go with the Wilshire 5000, which doesn't have the problem of being branded a "managed" fund, and it gives at least a little exposure to small and midcap stocks.

I personally would also eliminate the bond fund allocation if I was investing long-term (i.e. more than 5 years), especially considering that interest rates seem more likely to rise rather than fall, which would hurt bond prices and therefore bond funds.

Also, the international allocation isn't necessarily a bad idea, but it isn't likely to help much. It doesn't provide as much diversification as you would think, returns have lagged the US markets over the last 30 years, and expenses tend to be higher on international funds.