If the number of BTC suddenly doubled, you'd expect the value of each one to halve given rational expectations and perfect knowledge of BTC holders. Of course

If the number of BTC suddenly doubled, you'd expect the value of each one to halve given rational expectations and perfect knowledge of BTC holders. Of course a) the two BTC variants won't have equal worth and b) participants in the BTC economy have neither perfect knowledge nor total rationality (the level of rationality in the BTC ecosystem has been much debated over recent years as we all know) so the actual outcome may differ from the 'perfect' one, but the likelihood is that values will converge over time to the outcome that the value of BTC1+BTC2 post split is equal to the value of BTC pre-split, plus or minus any gains/losses along the way (which may include a reputational loss or gain based on how well the split goes).