It may be a handheld replacement someday. Scott's right that they've said that's not the plan, but plans can change, or maybe they're just being cagey about admitting to it. Because if that's their plan down the road, it's still in their best interest to not tip their hand while they're trying to sell 3DS's until they're really ready to position the Switch as the replacement.
But yeah, I definitely wouldn't gamble on that this early. I just wouldn't rule it out for the future. We also still don't know what the Virtual Console landscape will look like. One would hope the VC will at least match the capabilities and library of the 3DS, but again—better to be certain before pulling the trigger if that's what you want it for most.