Development happened very rapidly in the first two years of Apple. Wozniak did the Apple 1 in 1975 and the Apple ][ in 1976. When the Apple 1 was first presented to the world at the Homebrew Computer Club, it didn't have any name at all, since there was no company called "Apple" at the time. The original thought Woz had was simply to show off the computer he had designed to the club and share the schematics for the design - it was very much a "hacker" community project without thought of a commercial product.
Based on the interest in the Apple 1 design amongst the hacker/hobbyist community, Steve Jobs suggested ordering PCB's and selling them at a profit. While pursuing buyers for the PCB, Jobs made the famous deal with the Byte Shop in Palo Alto, but that deal required fully assembled PCB's to be delivered. This led to Jobs seeking capital from banks, arranging for vendor credit, and other similar business activities needed to launch a real product. So the company was officially founded and named "Apple", and shortly after Mike Markkula got involved and formed Apple, the Corporation.
While this was happening, Woz was already well on his way to developing the successor Apple ][. So the "Apple 1" was named with full knowledge that a company was being formed and would, hopefully in short order, be able to offer the far-superior Apple ][ to its customers.
This quote from a lengthy interview with Wozniak sums up the thinking of the Apple founders at the time:
I went to a store in Southern California, cause I was on vacation, showed them the Apple I, what it was, isn't that, demonstrated it. Got some orders out of that. But it was pretty much, you know, one person at a time, you know, getting small accounts. So we didn't sell very many in the period of a year. And by then, we had the Apple II. We even saw the Apple II coming and part of the Apple II introduction was, we said, you can turn in your Apple I for a real good refund or a discount on the Apple II.
Also, despite the fact that a successor to the Apple 1 was already planned, the company did exercise some discretion in not giving too much away when marketing the Apple 1. It was their only source of income for some months, so the little bit of marketing material that was created simply referred to the Apple 1 as "The Apple Computer".