Over time, web sites and shopping carts have become more accessible with features and functions to allow simplicity and easier navigation. This said, reviews today should be thorough enough to measure how you may grow later and whether you could keep the existing software choice.
Investigate agencies with e-commerce experience if you plan to outsource. Too often an agency has difficulties with data files that need to be transferred into Order Management Software. So always include any outsourcing decision in the initial web and cart reviews before implementation.
And if you do plan to outsource fulfillment, simply inquire about integrations. Most fulfillment companies have a number of existing integrations. This always speeds up any set up necessary to accept order data files. And today, integrations can be done in a relatively short period of time with a properly mapped file structure.