It does depend. Investing to other cryptos would yield to loss especially if the coin you would invest won't be able to jive with the uprise, if ever such thing would occur. Some people would say "Why would I invest into something that won't be profitable?", that's the point. In this industry, volatility is in nature and therefore, profit is not always certain given that changes may occur from time to time. Speculations won't give you assurance. So at some point, investing only to Bitcoin would be a better idea due to its reputation for long term holding.